Active matrix substrate, display device, and method for manufacturing active matrix substrate

ABSTRACT

An active matrix substrate  40  according to the present invention includes a conductive film  44  and a wiring  80  for supplying a signal to the conductive film  44 , characterized in that the wiring  80  includes a first conductive layer  61  and a second conductive layer  62  having a relatively large line width in comparison with the first conductive layer  61  and laminated so as to cover the first conductive layer  61 , and the conductive film  44  is arranged in a matrix pattern, and at least a portion of the conductive film  44  is disposed overlapping the wiring  80.

TECHNICAL FIELD

The present invention relates to an active matrix substrate, a displaydevice, and a method for manufacturing an active matrix substrate.

BACKGROUND ART

Recently, as high definition television receivers or large televisionreceivers spread rapidly, there is an increasing demand for highdefinition display devices. Liquid crystal displays (LCD) are one of theleading flat panel displays (FPD) along with electro luminescence (EL)displays and plasma display panels (PDP). The liquid crystal displayshave advantages of light weight, space-saving, low cost, low energyconsumption or the like.

At present, most of the liquid crystal displays used in the highdefinition television receivers or large television receivers aretransmissive liquid crystal displays. The transmissive liquid crystaldisplays have a configuration in which liquid crystal is held betweentwo glass substrates each having an electrode formed thereon. A liquidcrystal molecular orientation in a liquid crystal layer is changed by avoltage applied to the electrodes formed on the inner sides of thesubstrates. The optical characteristics of the liquid crystal layer arechanged based on the change in liquid crystal molecular orientation asdescribed above. Accordingly, from an orientation relationship with apolarizing plate fixed on the substrate, a transmitted light intensityfrom a backlight is adjusted to display an image.

Although the transmissive liquid crystal displays are broadly dividedinto a passive type and an active type from the standpoint of a drivingmethod, most of the present transmissive liquid crystal displays are theactive type. In the active type liquid crystal displays, a switchingelement is provided in each pixel, and the operation of each pixel isthereby controlled. A three-terminal thin film transistor (TFT) is oftenused as the switching element.

An active matrix substrate where active elements such as the thin filmtransistors are formed over the entire surface is manufactured byrepeating processes of photolithography and etching a plurality oftimes. That is, a gate wiring, a gate insulating film, a semiconductorlayer, a source wiring, a drain wiring, an interlayer insulating film,and a pixel electrode are sequentially laminated respectively by thephotolithography process, the etching process or the like.

Meanwhile, display characteristics such as high brightness andvisibility are required in this type of liquid crystal display. Variousefforts have been made to improve a so-called aperture ratio. Forexample, a technique disclosed in Patent Document 1 is one of theexamples. In Patent Document 1, a pixel electrode is providedoverlapping a gate wiring or a source wiring that is a light shieldingportion, to thereby increase the aperture ratio and improve the displaycharacteristics.

[Patent Document 1] Japanese Patent Laid-Open No. 2007-52040

Problems to be Solved by the Invention

Meanwhile, in the case where a pixel electrode overlaps a wiring via aninterlayer insulating film as in the technique disclosed in PatentDocument 1, a leak may occur between the pixel electrode and the wiringto cause a display failure due to a point defect if a film defect occursin the interlayer insulating film. Especially when the interlayerinsulating film includes only one layer, such a film defect occurs moreeasily.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the aforementionedproblems, and it is an object of the present invention to provide anactive matrix substrate in which a drive failure is difficult to occurby preferably preventing or suppressing a trouble that leak occursbetween conductive films even when a defect occurs in an insulating filminterposed between the conductive films at a portion where theconductive films overlap each other, and a manufacturing method thereof.Also, it is another object of the present invention to provide a highlyreliable display device which uses the above active matrix substrate.

Means for Solving the Problems

In order to achieve the above object, an active matrix substrateaccording to the present invention includes a conductive film, and awiring for supplying a signal to the conductive film, characterized inthat the wiring includes a first conductive layer and a secondconductive layer having a relatively large line width in comparison withthe first conductive layer and laminated so as to cover the firstconductive layer, and the conductive film is arranged in a matrixpattern, and at least a portion of the conductive film is disposedoverlapping the wiring.

With the active matrix substrate, a portion of the conductive filmoverlaps the wiring where the second conductive layer covers the firstconductive layer having a relatively small line width. Therefore, evenwhen the conductive film and the wiring directly contact each other dueto, for example, a film defect or the like occurring in an insulatingfilm interposed between the wiring and the conductive film at theoverlapping portion, the second conductive layer having a large linewidth causes the conductive film to be cut off. It is thereby possibleto prevent a leak between the conductive film (a portion which is notoverlapping the wiring) and the wiring. That is, a peripheral portion ofthe second conductive layer projecting from the first conductive layercauses the conductive film to be cut off, to thereby insulate theportion of the conductive film which is overlapping the wiring from theportion which is not overlapping the wiring.

In the above active matrix substrate, the conductive film may overlapthe wiring via an interlayer insulating film. In the case where theconductive film overlaps the wiring via the interlayer insulating filmas described above, there is a risk that the conductive film and thewiring are connected to each other at a film defect position if a filmdefect occurs in the interlayer insulating film. Thus, in the case ofusing the interlayer insulating film, the wiring configuration includingthe first conductive layer and the second conductive layer as describedabove is employed. The leak between the conductive film and the wiringcan be thereby preferably prevented from occurring. The presentinvention is effective especially when the conductive film overlaps thewiring only via the interlayer insulating film.

The wiring configuration may be applied to a source wiring and/or a gatewiring. By preferably preventing the leak occurrence between the sourcewiring or the gate wiring and the conductive film, a signal can behighly reliably supplied to the conductive film from the source wiringor the gate wiring.

The first conductive layer may be mainly made of aluminum. In the casewhere the aluminum is used as described above, the first conductivelayer can be configured to have a preferably small width by wet etching.Also, the second conductive layer may be mainly made of titanium. In thecase where the titanium is used as described above, the secondconductive layer can be configured to have a preferably large width bydry etching. More preferably, a mask is formed on the second conductivelayer after forming the first conductive layer and the second conductivelayer in a laminated manner. Thereafter, the second conductive layer ispatterned by dry etching via the mask, and the first conductive layer ispatterned by wet etching via the same mask. Accordingly, theconfiguration according to the present invention can be preferablyachieved. Particularly, by performing side etching on the firstconductive layer by wet etching, the configuration according to thepresent invention in which the relatively wide second conductive layercovers the relatively narrow first conductive layer can be preferablyachieved. Note that “mainly” in the present invention means that themain component is a component having a largest content, and containedcomponents other than the main component are impurities.

The active matrix substrate may further include a switching elementconnected to the wiring, characterized in that the conductive film is apixel electrode connected to the switching element. The pixel electrodeoverlaps the wiring, so that an effective pixel area can be increased.Also, the wiring includes the narrow first conductive layer and the widesecond conductive layer in the overlapping portion according to thepresent invention, so that it is possible to preferably prevent the leakbetween the wiring and the pixel electrode.

Next, in order to achieve the above object, a display device accordingto the present invention includes the above active matrix substrate, anda counter substrate disposed opposite to the active matrix substrate.

With the display device, when there is a large conductive film area onthe active matrix substrate and the area is employed as the pixelelectrode, an aperture ratio can be increased. Accordingly, high qualitydisplay can be provided by improving the display brightness. Also,particularly, since the leak arising from the film defect or the like inthe insulating film is difficult to occur between the conductive filmand the wiring, a highly reliable display device can be achieved.

Next, in order to achieve the above object, a method for manufacturingan active matrix substrate according to the present invention includes:a wiring forming step including the steps of forming a first conductivelayer, forming a second conductive layer on the first conductive layer,patterning the second conductive layer by performing selective etchingon the second conductive layer with respect to a laminated film of thefirst conductive layer and the second conductive layer, and patterningthe first conductive layer into a shape with a smaller line width thanthat of the second conductive layer by performing selective etching onthe first conductive layer with respect to the laminated film of thefirst conductive layer and the second conductive layer after patterningthe second conductive layer; an interlayer insulating film forming stepof forming an interlayer insulating film on the second conductive layer;and a conductive film forming step of forming a conductive film arrangedin a matrix pattern on the interlayer insulating film such that theconductive film covers at least a portion of the second conductivelayer.

With the manufacturing method, the active matrix substrate according tothe present invention can be preferably manufactured. Particularly, withrespect to the laminated film having the first conductive layer and thesecond conductive layer, the second conductive layer is selectivelyetched as a first stage (an selective etchant is used for the secondconductive layer), and the first conductive layer is selectively etchedas a second stage (an selective etchant is used for the first conductivelayer). At this point, the first conductive layer is patterned to have asmaller line width than that of the second conductive layer. Thus, thewiring having a laminated structure in which the second conductive layercovers the first conductive layer can be provided. It is therebypossible to prevent occurrence of a trouble that the wiring(specifically, the second conductive layer) and the conductive filmdirectly contact each other and a leak occurs therebetween due to, forexample, a film defect occurring in the interlayer insulating film withrespect to the conductive film provided on the wiring (specifically, thesecond conductive layer) via the interlayer insulating film. That is,since the second conductive layer having a large line width causes theconductive film to be cut off, the leak between the conductive film (aportion which is not overlapping the wiring) and the wiring can beprevented. That is, a peripheral portion of the second conductive layerprojecting from the first conductive layer causes the conductive film tobe cut off, to thereby insulate the portion of the conductive film whichis overlapping the wiring from the portion which is not overlapping thewiring.

In the manufacturing method, the step of patterning the secondconductive layer and the step of patterning the first conductive layermay be respectively performed by etching by using the same mask. In thecase where the same mask is used as described above, the number of stepsis reduced to thereby reduce a manufacturing cost. Particularly, whenthe same mask is used, the first conductive layer can be reduced inwidth by side etching the first conductive layer. In this connection, itis preferable to pattern the second conductive layer by dry etching andthe first conductive layer by wet etching.

The first conductive layer may be formed by using aluminum. In the casewhere the aluminum is used as described above, the first conductivelayer can be configured to have a preferably small width by wet etching.Also, the second conductive layer may be formed by using titanium. Inthe case where the titanium is used as described above, the secondconductive layer can be configured to have a preferably large width bydry etching.

ADVANTAGES OF THE INVENTION

According to the present invention, the active matrix substrate in whicha drive failure is difficult to occur by preferably preventing orsuppressing a trouble that a leak occurs between conductive films evenwhen a defect occurs in an insulating film interposed between theconductive films at a portion where the conductive films overlap eachother, and the manufacturing method thereof can be provided.

Also, according to the present invention, the highly reliable displaydevice which uses the active matrix substrate can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically illustrating theconfiguration of a liquid crystal display device according to a presentembodiment;

FIG. 2 is a sectional view schematically illustrating the configurationof the liquid crystal display device in FIG. 1;

FIG. 3 is a sectional view illustrating the main portion configuration(a portion of a liquid crystal panel) of the liquid crystal displaydevice in FIG. 1;

FIG. 4 is a plan view illustrating the pixel configuration of the liquidcrystal display device in FIG. 1;

FIG. 5 is a sectional view taken along a line A-A′ in FIG. 4;

FIG. 6 is a sectional view taken along a line B-B′ in FIG. 4;

FIG. 7 is a sectional view taken along a line C-C′ in FIG. 4;

FIG. 8 is a sectional view taken along the line C-C′ in FIG. 4 andillustrating a state in which a film defect occurs;

FIG. 9 is an explanatory view illustrating one step according to amethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 10 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 11 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 12 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 13 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 14 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 15 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 16 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 17 is an explanatory view illustrating one step according to themethod for manufacturing the liquid crystal display device in FIG. 1;

FIG. 18 is a sectional view taken along a line D-D′ in FIG. 4; and

FIG. 19 is a sectional view taken along the line D-D′ in FIG. 4 andillustrating a state in which a film defect occurs.

DESCRIPTION OF SYMBOLS

-   -   10 . . . Liquid crystal display device (Display device), 11 . .        . Liquid crystal panel (Display panel), Backlight unit, 30 . . .        Counter substrate, 40 . . . Element substrate (Active matrix        substrate), 41 . . . Glass substrate (Substrate), 44 . . . Pixel        electrode (Conductive film), 44 a, 44 b . . . Overlapping        portion, 49 . . . Pixel, 50 . . . Liquid crystal layer, 60 . . .        Thin film transistor (Switching element), 61 . . . First        conductive layer (Aluminum layer), 62 . . . Second conductive        layer (Titanium layer), 63 . . . Source wiring, 64 . . . Drain        electrode, 65 . . . Gate electrode, 66 . . . Gate insulating        film, 67 . . . Silicon film, 67 a . . . Channel region, 70 . . .        Interlayer insulating film, 71 . . . Ohmic layer, 80 . . .        Source wiring (Wiring), 90 . . . Gate wiring (Wiring)

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, an embodiment of a display device according to thepresent invention will be described with reference to the drawings.

FIG. 1 is a perspective view schematically illustrating theconfiguration of a liquid crystal display device according to thepresent embodiment. FIG. 2 is a sectional view schematicallyillustrating the configuration of the liquid crystal display device.FIG. 3 is a sectional view illustrating the main portion configuration(a portion of a liquid crystal panel) of the liquid crystal displaydevice. FIG. 4 is a plan view illustrating the pixel configuration ofthe liquid crystal display device. FIG. 5 is a sectional view takenalong a line A-A′ in FIG. 4. FIG. 6 is a sectional view taken along aline B-B′ in FIG. 4. FIG. 7 is a sectional view taken along a line C-C′in FIG. 4. FIG. 8 is a sectional view taken along the line C-C′ in FIG.4 and illustrating a state in which a film defect occurs.

A liquid crystal display device (a display device) 10 shown in FIGS. 1and 2 includes a rectangular liquid crystal panel 11, and a backlightunit 12 that is an external light source, which are integrally held by abezel 13 or the like.

The backlight unit 12 is a so-called direct type backlight unit. Thebacklight unit 12 has a configuration in which light sources (here, coldcathode tubes 17) are disposed parallel to each other directly below theback surface of the panel surface (the display surface) of the liquidcrystal panel 11 along the panel surface. The backlight unit 12 includesa metal base 14 having a rectangular substantially-box shape whose uppersurface side opens, a plurality of optical members 15 (a diffusingplate, a diffusing sheet, a lens sheet, and a reflection polarizingplate in the order from the lower side in the drawing) mounted so as tocover the opening portion of the base 14, a frame 16 for holding theoptical members 15 on the base 14, the cold cathode tubes 17 as lampshoused in the base 14, rubber (for example, silicon rubber) holders 18for holding the both end portions of the cold cathode tubes 17, lampholders 19 for holding the group of cold cathode tubes 17 and the groupof holders 18 together, and lamp clips 20 for holding the intermediateportions of the cold cathode tubes 17 excluding the both end portions.

As shown in FIG. 3, the liquid crystal panel 11 has a configuration inwhich a pair of substrates 30 and 40 are adhered to each other with apredetermined gap therebetween and liquid crystal is enclosed betweenthe both substrates 30 and 40. The liquid crystal forms a liquid crystallayer 50.

The substrate 40 is an element substrate (an active matrix substrate).The substrate 40 includes a thin film transistor (TFT, a switchingelement) 60 as a semiconductor element formed on the liquid crystallayer 50 side of a glass substrate 41, a pixel electrode 44 electricallyconnected to the thin film transistor 60, and an orientation film 45formed on the liquid crystal layer 50 side of the thin film transistor60 and the pixel electrode 44. A polarizing plate 42 is provided on theopposite side from the liquid crystal layer 50 side of the glasssubstrate 41.

The pixel electrode 44 includes a transparent conductive film such asITO (indium tin oxide), for example, and is formed in a matrix-likepattern on the liquid crystal layer 50 side of the element substrate 40.To be more specific, the pixel electrode 44 is connected to a drainelectrode 64 (see FIGS. 4 and 5) of the thin film transistor 60, and avoltage is selectively applied thereto by the switching operation of thethin film transistor 60. Also, the orientation film 45 is formed of apolyimide rubbing orientation film, for example. An object obtained byinstilling iodine or dye into a transparent film and extending the filmin one direction is employed as the polarizing plate 42, for example.

Meanwhile, the substrate 30 is a counter substrate. The substrate 30includes a color filter 33 formed on the liquid crystal layer 50 side ofa glass substrate 31 and having coloring portions R (red), G (green),and B (blue) that can selectively transmit light of respective colors R,G, and B, a counter electrode 34 formed on the liquid crystal layer 50side of the color filter 33, and an orientation film 35 formed on theliquid crystal layer 50 side of the counter electrode 34. A polarizingplate 32 is provided on the opposite side from the liquid crystal layer50 side of the glass substrate 31.

The color filter 33 includes a black matrix BM disposed at the boundaryof the coloring portions R, G, and B. The black matrix BM is disposedoverlapping a non-pixel portion of the element substrate 40 (that is, aregion where the thin film transistor 60 is formed) so as to cover thenon-pixel portion. Also, the counter electrode 34 includes a transparentconductive film such as ITO (indium tin oxide), for example, and isformed in an overall solid pattern on the liquid crystal layer 50 sideof the counter substrate 30. Also, the orientation film 35 is formed ofa polyimide rubbing orientation film, for example. An object obtained byinstilling iodine or dye into a transparent film and extending the filmin one direction is employed as the polarizing plate 32, for example.

As described above, the liquid crystal display device 10 according tothe present embodiment includes the thin film transistor 60 as thesemiconductor element, and a pixel including the thin film transistor 60has a configuration as shown in FIG. 4.

In the liquid crystal display device 10 according to the presentembodiment, a plurality of pixels 49 are configured in a matrix pattern,and the thin film transistor 60 is formed in each of the pixels 49 asthe semiconductor element for pixel switching.

The thin film transistor 60 includes a source electrode 63, the drainelectrode 64, and a gate electrode 65. A source wiring 80 for supplyingan image signal is connected to the source electrode 63. The imagesignal to be written into the source wiring 80 may be line-sequentiallysupplied, or each group of image signals may be supplied to a pluralityof source wirings 80 adjacent to each other. The source wiring 80 isconnected to a driving circuit for supplying the image signal to thepixel electrode 44 via a contact hole 68.

Also, a gate wiring 90 is connected to the gate electrode 65 of the thinfilm transistor 60. It is configured such that a scanning signal isline-sequentially applied in a pulse to the gate wiring 90 at apredetermined timing.

The pixel electrode 44 is connected to the drain electrode 64 of thethin film transistor 60 via the contact hole 68. When the thin filmtransistor 60 as the switching element is brought into an ON state for agiven period of time, the image signal supplied from the source wiring80 is written into each pixel 49 at a predetermined timing. The imagesignal at a predetermined level written into the liquid crystal via thepixel electrode 44 as described above is maintained for a given periodof time between the pixel electrode 44 and the counter electrode 34 (seeFIG. 3). Here, to prevent the maintained image signal from leaking, astorage capacity (not shown) is additionally provided parallel to aliquid crystal capacity formed between the pixel electrode 44 and thecounter electrode 34 (see FIG. 3).

Also, in the present embodiment, in order to increase an aperture ratio,the pixel electrode 44 includes an overlapping portion 44 a where thepixel electrode 44 overlaps the source wiring 80, and an overlappingportion 44 b where the pixel electrode 44 overlaps the gate wiring 90.That is, by forming the pixel electrode 44 in a matrix pattern so as tooverlap the respective wirings 80 and 90 in plan view, bright andhigh-quality display can be achieved.

As described above, the thin film transistor 60 is provided on the glasssubstrate 41 constituting the element substrate 40. To be more specific,as shown in FIG. 5, the thin film transistor 60 includes the gateelectrode 65 formed on the glass substrate 41, a gate insulating film 66formed on the gate electrode 65, a silicon film 67 formed on the gateinsulating film 66 and having a channel region 67 a, an ohmic layer 71formed on the silicon film 67, the source electrode 63 connected to oneend of the silicon film 67, and the drain electrode 64 connected to theother end of the silicon film 67 and connected to the source electrode63 via the channel region 67 a.

The gate electrode 65 and the gate wiring 90 connected to the gateelectrode 65 can be formed of a single metal film of chromium (Cr),tantalum (Ta), titanium (Ti) or the like in addition to aluminum (Al),or a laminated film thereof, for example.

The gate insulating film, 66 can be formed of silicon oxide (SiOx) orthe like in addition to silicon nitride (SiNx), for example.

The silicon film 67 can be formed of amorphous silicon (a−Si) or thelike, for example.

The ohmic layer 71 can be formed of amorphous silicon (n+Si) heavilydoped with n-type impurities such as phosphorus (P) or the like, forexample.

Each of the source electrode 63, the drain electrode 64, and the sourcewiring 80 connected to the source electrode 63 is configured as alaminated film where a first conductive layer 61 and a second conductivelayer 62 are laminated (see FIG. 7). The first conductive layer 61 onthe lower layer side is formed of aluminum (Al). The second conductivelayer 62 on the upper layer side is formed of titanium (Ti). The secondconductive layer 62 has a relatively large line width in comparison withthe first conductive layer 61, and is laminated so as to cover the firstconductive layer 61.

Also, an interlayer insulating film (a passivation film) 70 is formed onthe source electrode 63, the drain electrode 64, the source wiring 80and the gate wiring 90. The drain electrode 64 is connected to the pixelelectrode 44 via the contact hole 68 formed in the interlayer insulatingfilm 70 (see FIG. 6). The interlayer insulating film 70 can be formed ofan acrylic resin film or the like in addition to an inorganic insulatingfilm such as silicon nitride (SiNx), for example.

In the liquid crystal display device 10 according to the presentembodiment as described above, the pixel electrode 44 formed on theelement substrate (the active matrix substrate) 40 includes theoverlapping portion 44 a where the pixel electrode 44 overlaps thesource wiring 80, and the source wiring 80 includes the first conductivelayer 61 and the second conductive layer 62 as particularly shown inFIG. 7. The second conductive layer 62 having a relatively large linewidth is configured to cover the first conductive layer 61 having asmall line width. Thus, as shown in FIG. 8, even when the pixelelectrode 44 and the source wiring 80 directly contact each other due toa film defect or the like occurring in the interlayer insulating film 70interposed between the pixel electrode 44 and the source wiring 80 atthe portion where the pixel electrode 44 overlaps the source wiring 80,the second conductive layer 62 having a large line width causes thepixel electrode 44 to be cut off. Thus, it is possible to prevent a leakbetween the pixel electrode 44 (a portion 44 c which is not overlappingthe source wiring 80) and the source wiring 80. That is, a peripheralportion of the second conductive layer 62 projecting from the firstconductive layer 61 causes the film of the pixel electrode 44 to be cutoff, to thereby insulate the portion 44 a of the pixel electrode 44which is overlapping the source wiring 80 from the portion 44 c which isnot overlapping the source wiring 80 as shown in the drawing. Note thatthe film defect means a local separation of a first portion 70 a and asecond portion 70 b due to the interlayer insulating film 70 being cutoff at an edge portion of the source wiring 80 as shown in FIG. 8.

Next, a method for manufacturing the liquid crystal display device 10according to the present embodiment will be described. Here, steps ofmanufacturing the element substrate 40 in the manufacturing method willbe particularly described with reference to FIGS. 9 to 17. In FIGS. 9 to17, the left side in the drawing illustrates the manufacturing stepsrelative to the section along A-A′ in FIG. 4, and the right side in thedrawing illustrates the manufacturing steps relative to the sectionalong c-C′ in FIG. 4.

First, as shown in FIG. 9, the glass substrate 41 is prepared. The gateelectrode 65 is formed on the glass substrate 41. The gate electrode 65can be formed by patterning, by mask etching using a photolithographymethod, a conductive film which is formed by a sputtering method, forexample. To be more specific, a conductive film having a laminated filmof three layers titanium-aluminum-titanium is patterned by wet etching.

Subsequently, as shown in FIG. 10, the gate insulating film 66, a firstsilicon film (amorphous silicon (a−Si)) 167, and a second silicon film(n+Si) 171 are formed on the gate electrode 65 respectively by a plasmaCVD method, for example. The gate insulating film 66 can be formed ofsilicon oxide (SiOx) or the like in addition to silicon nitride (SiNx),for example.

Subsequently, as shown in FIG. 11, the first silicon film 167 and thesecond silicon film 171 formed above are patterned by mask etching usinga photolithography method. To be more specific, the first silicon film167 and the second silicon film 171 are patterned by dry etching.Accordingly, the first silicon film 167 and the second silicon film 171having patterns as shown in FIG. 11 are formed.

Subsequently, as shown in FIG. 12, a conductive film 161 made ofaluminum and a conductive film 162 made of titanium are formed by asputtering method. A laminated film of the conductive film 161 and theconductive film 162 is patterned by using a mask 100 as shown in FIG.13.

To be more specific, the conductive film 162 disposed on the upper layerside is patterned by dry etching, first. The second conductive layer 62is thereby formed as shown in FIG. 14. After that, the conductive film161 disposed on the lower layer side is patterned by wet etching (amixture of phosphoric acid, nitric acid, and acetic acid is used as anetching solution) by using the same mask 100. At this point, theconductive film 161 is side-etched by a predetermined amount, so thatthe first conductive layer 61 is formed as shown in FIG. 15. That is,the first conductive layer 61 covered by the second conductive layer 62having a relatively large line width is formed. The second silicon film171 is dry-etched by using the same mask 100, so that the silicon film67 and the ohmic layer 71 having patterns as shown in FIG. 16 areformed.

Subsequently, the interlayer insulating film 70 is formed by a plasmaCVD method as shown in FIG. 17 after removing the mask 100. Theinterlayer insulating film 70 and the gate insulating film 66 describedabove are patterned by mask etching (specifically, dry etching) using aphotolithography method. Thereafter, an ITO film is further formed bysputtering, and is patterned by mask etching (specifically, wet etching)using a photolithography method. The pixel electrode 44 is therebyformed. At this point, the pixel electrode 44 is patterned such that theoverlapping portions 44 a and 44 b are particularly formed with respectto the source wiring 80 and the gate wiring 90.

The element substrate 40 manufactured by the above method is adhered tothe counter substrate 30 manufactured by another method via a sealingagent (not shown). The liquid crystal is injected into a space betweenthe substrates, and an injection port (not shown) is sealed. Thepolarizing plates 32 and 42 are respectively adhered to the substrates30 and 40. The liquid crystal panel 11 as shown in FIG. 3 is therebycompleted. After that, the backlight unit 12 is mounted on the liquidcrystal panel 11 via the bezel 13 or the like, so that the liquidcrystal display device 10 as shown in FIGS. 1 and 2 is completed.

With the manufacturing method as described above, with respect to thelaminated film of the conductive film 161 and the conductive film 162,the second conductive layer 62 is formed by selectively etching theconductive film 162 as a first stage, and the first conductive layer 61having the pattern with a smaller line width than the second conductivelayer 62 is formed by side etching at the time of selectively etchingthe conductive film 161 as a second stage. Accordingly, the sourcewiring 80 having a laminated structure in which the second conductivelayer 62 covers the first conductive layer 61 is provided. That is, theelement substrate 40 having the configuration according to theaforementioned embodiment can be preferably manufactured.

Although the configuration of the source wiring 80 is described above,the gate wiring 90 may be also constituted by a laminated wiring. To bemore specific, as shown in the section along a line D-D′ (see FIG. 4) inFIGS. 18 and 19, the gate wiring 90 includes the laminated wiring. Here,a conductive layer 65 a made of titanium, a conductive layer 65 b madeof aluminum, and a conductive layer 65 c made of titanium in the orderfrom the lower layer constitute the gate wiring 90. In this case, theconductive layer 65 c on the upper layer side is also formed to have alarger line width than the conductive layer 65 b on the lower layerside, and cover the conductive layer 65 b on the lower layer side. Thepixel electrode 44 is formed overlapping the gate wiring 90.

In this case, for example, as shown in FIG. 19, even when the pixelelectrode 44 and the gate wiring 90 directly contact each other due to afilm defect or the like occurring in the interlayer insulating film 70interposed between the pixel electrode 44 and the gate wiring 90 at aportion where the pixel electrode 44 overlaps the gate wiring 90, theconductive layer 65 c having a large line width also causes the pixelelectrode 44 to be cut off. Thus, it is possible to prevent a leakbetween the pixel electrode 44 (a portion 44 b which is not overlappingthe gate wiring 90) and the gate wiring 90. That is, a peripheralportion of the conductive layer 65 c projecting from the conductivelayer 65 b causes the film of the pixel electrode 44 to be cut off, tothereby insulate the portion 44 b of the pixel electrode 44 which isoverlapping the gate wiring 90 from the portion 44 d which is notoverlapping the gate wiring 90 as shown in the drawing.

In order to form the conductive layer 65 c on the upper layer side andthe conductive layer 65 b on the lower layer side such that theconductive layer 65 c covers the conductive layer 65 b, dry etching andwet etching (side etching) are performed by the same mask as describedabove to thereby achieve a laminated structure. However, the laminatedstructure may be also achieved even when dry etching is continuouslyperformed, for example. That is, by employing different etchingconditions between the conductive layer 65 c on the upper layer side andthe conductive layer 65 b on the lower layer side, specifically,employing different pressures inside a chamber, different RP powers,different flow rates of chlorine gas or the like between the conductivelayers 65 c and 65 b, the laminated structure as shown in FIG. 18 can beprovided. For example, when the conductive layer 65 b made of aluminumon the lower layer side is etched, the pressure in the chamber isincreased, the RP power is decreased and the flow rate of chlorine gasis increased in comparison with the case of etching the conductive layer65 c made of titanium on the upper layer side. The conductive layer 65 bon the lower layer side can be thereby patterned to have a smaller linewidth than the conductive layer 65 c on the upper layer side. The linewidth adjustment of each layer in the laminated wiring by using dryetching as described above can be also applied to when the firstconductive layer 61 and the second conductive layer 62 of the sourcewiring 80 are patterned.

Although one embodiment according to the present invention is describedabove, the present invention should not be limited to the embodiment asdescribed above.

For example, in the present embodiment, the liquid crystal displaydevice having the thin film transistor is described as one example ofthe display device according to the present invention. However, forexample, an EL display and a plasma display panel or the like drivingthe pixel and having the thin film transistor similar to the presentembodiment are also included in the present invention.

1. An active matrix substrate comprising a conductive film, and a wiringfor supplying a signal to the conductive film, characterized in that thewiring comprises a first conductive layer and a second conductive layerhaving a relatively large line width in comparison with the firstconductive layer and laminated so as to cover the first conductivelayer, and the conductive film is arranged in a matrix pattern, and atleast a portion of the conductive film is disposed overlapping thewiring.
 2. The active matrix substrate according to claim 1,characterized in that the conductive film overlaps the wiring via aninterlayer insulating film.
 3. The active matrix substrate according toclaim 1, characterized in that the wiring is a source wiring.
 4. Theactive matrix substrate according to claim 1, characterized in that thewiring is a gate wiring.
 5. The active matrix substrate according toclaim 1, characterized in that the first conductive layer is mainly madeof aluminum.
 6. The active matrix substrate according to claim 1,characterized in that the second conductive layer is mainly made oftitanium.
 7. The active matrix substrate according to claim 1, furthercomprising a switching element connected to the wiring, characterized inthat the conductive film is a pixel electrode connected to the switchingelement.
 8. A display device comprising the active matrix substrateaccording to claim 1, and a counter substrate disposed opposite to theactive matrix substrate.
 9. A method for manufacturing an active matrixsubstrate comprising: a wiring forming step comprising the steps offorming a first conductive layer, forming a second conductive layer onthe first conductive layer, patterning the second conductive layer byperforming selective etching on the second conductive layer with respectto a laminated film of the first conductive layer and the secondconductive layer, and patterning the first conductive layer into a shapewith a smaller line width than that of the second conductive layer byperforming selective etching on the first conductive layer afterpatterning the second conductive layer; an interlayer insulating filmforming step of forming an interlayer insulating film on the secondconductive layer; and a conductive film forming step of forming aconductive film arranged in a matrix pattern on the interlayerinsulating film such that the conductive film covers at least a portionof the second conductive layer.
 10. The method for manufacturing anactive matrix substrate according to claim 9, characterized in that thestep of patterning the second conductive layer and the step ofpatterning the first conductive layer are respectively performed byetching by using a same mask.
 11. The method for manufacturing an activematrix substrate according to claim 9, characterized in that the secondconductive layer is patterned by dry etching and the first conductivelayer is patterned by wet etching.
 12. The method for manufacturing anactive matrix substrate according to claim 9, characterized in that thefirst conductive layer is formed by using aluminum.
 13. The method formanufacturing an active matrix substrate according to claim 9,characterized in that the second conductive layer is formed by usingtitanium.